Kiev will be firing missiles across the disputed sea in a move Russia warned could trigger a rapid escalation in hostilities.

Konstantin Kosachev, chairman of the foreign policy committee in Russia”s parliament, said: “If the situation escalates to the point where a military response is necessary, this will surely be the most frightening and undesirable scenario of events, which all of us should prevent at all costs.”

The senator added: “I”d place an accent on the phrase “all of us” because that”s not exclusively Russia”s problem.”

Putin is personally keeping a close eye on the boiling conflict in the region, according to Kremlin spokesman Dmitry Peskov.

Sergei Zheleznyak, a member of Russia”s State Duma Committee for International Affairs, said Ukraine”s “irresponsible and unreasonable actions” were a cause of “great concern”.

“The presence of the Russian regular army on the territory of Ukraine varies from 5,000 to 7,500 soldiers.

“In Crimea, this figure is 23,000 troops, of which 9,000 are on the administrative border.”

NATO bosses fear a full US withdrawal from the military pact following the election of Donald Trump would pave the way for a Russian invasion of Eastern Europe – with the alliance preparing for a “worst case scenario“.